Natural wonder Asia
Semeru
Semeru is the highest volcano on the island of Java, in Indonesia. It is one of Indonesia's most active volcanoes.
Semeru is a stratovolcano on the island of Java, in Indonesia. NASA calls it Java's highest volcano, rising 3,676 meters above the nearby coastal plains, and one of Indonesia's most active volcanoes.
Semeru, in East Java, is a stratovolcano of alternating layers of solidified lava, hardened ash and volcanic rock (NASA). It rises 3,676 m above the nearby coastal plains, ranks among Indonesia's most active volcanoes and is part of the Pacific Ring of Fire.
Photo: M Joko Apriyo Putro, CC BY-SA 4.0, via Wikimedia Commons
Discover Semeru
Semeru is a volcano on Java, an island in Indonesia. It is the highest volcano on Java.
In this photo, a cloud sits on top of the cone, and fields and trees grow below.
Semeru is in East Java, Indonesia. NASA calls it Java's highest volcano, rising 3,676 meters above the nearby coastal plains, and says it ranks among Indonesia's most active volcanoes.
This photo by M Joko Apriyo Putro, taken in December 2021, shows the cone with a red glow and a cloud at the top, forest on its lower slopes and farm fields in front.
NASA's Earth Observatory describes Semeru as Java's highest volcano, rising 3,676 m above the nearby coastal plains, and among Indonesia's most active. Java's volcanoes are part of the Ring of Fire, an area of heightened seismic activity around the Pacific Ocean basin.
The hero photo (M Joko Apriyo Putro, CC BY-SA 4.0) was taken in December 2021: a dark cone with a red glow and a cloud at the summit, forested lower slopes and fields in the foreground.
- Height
- 3,676 m above the nearby coastal plains
- Type
- stratovolcano
- Where
- East Java, Indonesia
A cone built in layers
Semeru is made of layers of lava, ash and rock.
The layers lie one on top of another.
NASA explains that Semeru is a stratovolcano, made of alternating layers of solidified lava, hardened ash and volcanic rocks.
The volcanoes of Java are part of the Ring of Fire, an area of heightened earthquake activity around the Pacific Ocean. NASA notes that Semeru erupted in 2006 as part of a larger pattern of earthquake activity on Java.
Semeru is a stratovolcano composed of alternating layers of solidified lava, hardened ash and volcanic rocks (NASA, 2007). Java's volcanoes lie in the 'Ring of Fire', an area of heightened seismic activity around the Pacific Ocean basin (NASA, 2006).
NASA links Semeru's 2006 eruption to a larger pattern of seismic activity on Java: three days after an earthquake struck Java on 27 May 2006, the volcano showed signs of heightened activity.
Watching from space
Satellites in space take pictures of Semeru.
They can see ash clouds and hot spots.
On May 30, 2006, NASA's Terra satellite outlined Semeru's summit in red where it sensed unusually high surface temperatures, with gray-brown clouds to the west that could have been ash.
On May 3, 2007, the same satellite photographed a gray-beige plume from Semeru blowing west over Java.
The MODIS instrument on NASA's Terra satellite detected unusually high surface temperatures at Semeru's summit on 30 May 2006, with gray-brown clouds to the west that 'could result from volcanic ash'.
On 3 May 2007 MODIS imaged an opaque, gray-beige plume blowing west over Java, with bright white clouds scattered around the volcano.
Orchids and forests
Forests and many kinds of flowers grow around Semeru.
There are more than 200 kinds of orchids!
UNESCO's Bromo Tengger Semeru-Arjuno Biosphere Reserve in East Java, whose name includes Semeru, was named in 2015. UNESCO reports 1,025 kinds of plants there, including 226 kinds of orchids.
Some mammals in the reserve's core area are on the IUCN Red List of Threatened Species.
The Bromo Tengger Semeru-Arjuno Biosphere Reserve (UNESCO MAB, 2015; 413,375 ha) records 1,025 flora species, of which 226 are orchids and 260 are medicinal and ornamental plants; common plant families include Fagaceae, Moraceae and Anacardiaceae.
UNESCO notes that some mammal species in the core area are on the IUCN Red List of Threatened Species, and that livestock farming and tourism support the local economy.
Visiting safely
Always listen to the local officials near a volcano.
Volcanic ash can hurt your lungs, so cover your nose and mouth.
The US Centers for Disease Control and Prevention (CDC) says to follow the advice of local officials about a volcano, and be ready either to shelter or to leave the area. A kit should include breathing protection and goggles, because ash can harm your lungs.
Semeru rises to 3,676 meters. The CDC says altitude sickness can affect children just as adults, and going down at least 300 meters helps.
The CDC advises following local officials on preparing for an eruption and on whether to evacuate or shelter in place; emergency kits should include respiratory protection and eye protection (goggles), since exposure to ash can harm the respiratory tract.
The CDC's Yellow Book says any unacclimatized traveler sleeping at 2,450 m or higher is at risk of altitude illness, children are as susceptible as adults, and a descent of 300 m or more brings rapid improvement.
Amazing facts
-
Semeru is the highest volcano on the island of Java.
NASA calls Semeru Java's highest volcano, rising 3,676 meters above the nearby coastal plains.
NASA: Semeru is Java's highest volcano, 3,676 m above the nearby coastal plains, and ranks among Indonesia's most active.
-
More than 200 kinds of orchids grow in the area around Semeru.
UNESCO counts 226 kinds of orchids among the 1,025 plant species of the Bromo Tengger Semeru-Arjuno Biosphere Reserve.
Of the reserve's 1,025 recorded flora species, UNESCO lists 226 orchids and 260 medicinal and ornamental plants.
-
A satellite can see where a volcano's top is hot.
In 2006, NASA's Terra satellite outlined Semeru's summit in red where it sensed unusually high temperatures.
On 30 May 2006, MODIS detected unusually high surface temperatures at Semeru's summit, outlined in red on NASA's image.
Words to know
- stratovolcano
- a cone-shaped volcano built from layers of lava, ash and rock
- Ring of Fire
- the area around the Pacific Ocean with many earthquakes and volcanoes
- plume
- a cloud of ash and gas rising from a volcano
- biosphere reserve
- an area UNESCO recognizes for protecting nature while people live and work there
- orchid
- a flowering plant with many species, often with showy flowers
Discovery challenge
-
Which island is Semeru on?
On which island is Semeru the highest volcano?
Which island's highest volcano is Semeru, according to NASA?
- Java
- Iceland
- Hawaii
Show the answer
Java
Java, in Indonesia.
Java, in Indonesia.
Java: Semeru is the island's highest volcano (NASA).
-
What is Semeru made of?
What layers make up Semeru, according to NASA?
Which alternating layers compose Semeru as a stratovolcano?
- Layers of lava, ash and rock
- Layers of ice
- Layers of sand from the sea
Show the answer
Layers of lava, ash and rock
Layers of lava, ash and rock.
Solidified lava, hardened ash and volcanic rocks.
Alternating layers of solidified lava, hardened ash and volcanic rocks.
-
What did a satellite see at the top of Semeru in 2006?
What did NASA's Terra satellite detect at Semeru's summit in May 2006?
What did MODIS detect at Semeru's summit on 30 May 2006?
- A hot spot
- A frozen lake
- A new forest
Show the answer
A hot spot
A hot spot.
Unusually high surface temperatures, outlined in red.
Unusually high surface temperatures at the summit.
-
Which flowers have more than 200 kinds near Semeru?
Which plants have 226 species in the biosphere reserve around Semeru?
Which plant group accounts for 226 of the reserve's 1,025 flora species?
- Orchids
- Cactuses
- Water lilies
Show the answer
Orchids
Orchids.
Orchids: 226 species.
Orchids (226 species; UNESCO MAB).
-
Near a volcano, who should you listen to?
Whose advice does the CDC say to follow about a volcanic eruption?
What does the CDC advise about preparing for a volcanic eruption?
- Local officials
- Nobody
- Only your friends
Show the answer
Local officials
Local officials.
Local officials, about preparing and about when to shelter or leave.
Follow local officials on preparation, evacuation or sheltering, and keep respiratory and eye protection.
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For parents & teachers
What children will learn
- Locate Semeru on the island of Java in Indonesia.
- Explain how a stratovolcano is built from layers.
- Describe how satellites watch volcanoes for heat and ash.
- Know how to stay safe near an active volcano.
Recommended ages: 3 to 17 · About 15 minutes
Talk about it
- Why might a satellite be a good way to watch a volcano?
- Why do so many volcanoes lie around the Pacific Ocean?
- Why should people near a volcano follow local officials' advice?
Try at home or in class
- Layer colored sand, flour and fine gravel in a clear cup to model the lava, ash and rock layers of a stratovolcano.
- On a world map, trace the Ring of Fire around the Pacific Ocean and find Java on it.
Key vocabulary: stratovolcano, Ring of Fire, plume, biosphere reserve, orchid
Where these facts come from
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Volcanic Activity on Semeru , NASA Earth Observatory
- Volcanic Plume from Mount Semeru, Java , NASA Earth Observatory
- Bromo Tengger Semeru-Arjuno (Man and the Biosphere Programme) , UNESCO
- Staying Safe During a Volcanic Eruption , US Centers for Disease Control and Prevention
- High-Altitude Travel and Altitude Illness (CDC Yellow Book) , US Centers for Disease Control and Prevention
- File:Bentang Alam Gunung Semeru.jpg , Wikimedia Commons
- Wikimedia Commons , Wikimedia Foundation (Per file (public domain, CC0, CC BY or CC BY-SA); see each media record)
Checked, not yet human-reviewed. Last updated November 1, 2026. Spotted a mistake? Tell us.